The basic directional coupler is a linear, passive, four port network, consisting of a pair of coupled transmission lines. A first transmission line defines an input port and a thru port, and a second transmission line defines a coupled port and an isolation port. Propagation of a signal applied to the input port along the first transmission line induces the propagation of a coupled signal along the second transmission line. Maximum signal coupling between the pair of coupled transmission lines is achieved when the length of the coupling region is an odd multiple of a quarter wavelength. Because signal coupling is dependent on the signal wavelength, existing directional couplers are narrowly limited to a specific bandwidth. The ability to increase the operational bandwidth of a directional coupler would greatly increase the benefits of presently existing couplers and broaden their applications into other areas.